Open external links in browser

If a clicked links host doesn't match www.trello.com or trello.com it
will be opened with the default browser.
click dock icon to reopen the window
window now remembers location and size
Update README.md
Added exclusion for accouts.google.com when opening external links
Updated icon
Set default window size to 1440x900
Revert "Set default window size to 1440x900"

This reverts commit dba47d1d91a2aea558e770bef9bd1f9185c8dd94.
Merge 'Dovizu/master'

Changes:
- Click dock icon to reopen the window
- Window now remembers location and size
Xcode workspace